1. Field
The following description relates to a circuit for generating a boosted voltage which is higher than an input voltage, and a method for operating the boosted voltage generation circuit.
2. Description of Related Art
Diverse semiconductor devices operate internal circuits with a voltage supplied from the outside. As diverse levels of voltages are used in the internal constituent elements of a semiconductor device, it is difficult to supply all the voltages to be used in the inside of the semiconductor device from the outside of the device. Therefore, semiconductor devices are equipped with an internal voltage generation circuit to generate diverse levels of voltages inside the device.
Particularly, a device using a battery power source should be able to generate higher levels of voltage than the level of an input power source voltage inputted from the outside when the level of a power source voltage supplied from a battery is low and the levels of driving voltages to be used inside the device are higher than the level of the input power source voltage. DC-DC converters which generate a higher level of voltage than the level of input voltage are divided into a switched mode power supply (SMPS) type using an inductor and a charge pump type using a capacitor. In case of mobile devices, since the current consumption is not great, they are usually of the charge pump type.
Unlike a linear power supply, the pass transistor of an SMPS switches very quickly (typically between 50 kHz and 1 MHz) between full-on and full-off states, which minimizes wasted energy. Voltage regulation is provided by varying the ratio of on time to off time. In contrast, a linear power supply must dissipate the excess voltage to regulate the output. This higher efficiency is the chief advantage of the SMPS. Switching regulators are used as replacements for the linear regulators when higher efficiency, smaller size and/or lighter weight are required.
FIG. 1 is a block diagram showing voltage, signal, and output voltage of a boosted voltage generation circuit.
An input voltage VCIN and boosting rate BT[a:0] are inputted into the boosted voltage generation circuit 100. The boosted voltage generation circuit 100 boosts the input voltage VCIN based on the boosting rate represented by the boosting rate BT[a:0], and generates a boosted voltage VOUT. For example, when the boosting rate BT[a:0] is 2, which means two times or double, the boosted voltage generation circuit 100 boosts the input voltage VCIN two times (i.e., doubles the voltage), and generates the boosted voltage VOUT.
Although the target values of the boosted voltage VOUT are the same, there may be diverse input voltages VCIN and boosting rates BT[a:0] in the boosted voltage generation circuit 100. For instance, when the target value of the boosted voltage VOUT is 3V, (a) the boosted voltage VOUT of 3V may be generated by boosting an input voltage VCIN of 1.5V two times (i.e., doubling), or (b) the boosted voltage VOUT of 3V may be generated by boosting an input voltage VCIN of 1V three times (i.e., tripling). However, although the same boosted voltage VOUT is generated, the amount of current consumed by the boosted voltage generation circuit 100 may be greatly different based on how the input voltage VCIN and the boosting rate BT[a:0] are set.
However, conventional power supplies do not optimize the input voltage VCIN and the boosting rate BT[a:0] inputted into the boosted voltage generation circuit 100 according to the target level of the boosted voltage VOUT.